CN114397724A - Polarizing plate and liquid crystal display device comprising same - Google Patents

Polarizing plate and liquid crystal display device comprising same Download PDF

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Publication number
CN114397724A
CN114397724A CN202210116539.8A CN202210116539A CN114397724A CN 114397724 A CN114397724 A CN 114397724A CN 202210116539 A CN202210116539 A CN 202210116539A CN 114397724 A CN114397724 A CN 114397724A
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China
Prior art keywords
polyester film
polarizing plate
film
wavelength
axis direction
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Pending
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CN202210116539.8A
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Chinese (zh)
Inventor
申光浩
朴银洙
申东允
郑海龙
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Samsung SDI Co Ltd
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Samsung SDI Co Ltd
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Publication of CN114397724A publication Critical patent/CN114397724A/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G02B5/3041—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
    • G02B5/305—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks including organic materials, e.g. polymeric layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B29D11/00634—Production of filters
    • B29D11/00644—Production of filters polarizing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/38—Layered products comprising a layer of synthetic resin comprising epoxy resins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B33/00—Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04—Homopolymers or copolymers of esters
    • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09J133/08—Homopolymers or copolymers of acrylic acid esters
    • G—PHYSICS
    • G02—OPTICS
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    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528—Polarisers
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G02F1/133634—Birefringent elements, e.g. for optical compensation the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C63/00—Lining or sheathing, i.e. applying preformed layers or sheathings of plastics; Apparatus therefor
    • B29C63/48—Preparation of the surfaces
    • B29C2063/483—Preparation of the surfaces by applying a liquid
    • B29C2063/485—Preparation of the surfaces by applying a liquid the liquid being an adhesive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
    • B29C55/08—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique transverse to the direction of feed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C63/00—Lining or sheathing, i.e. applying preformed layers or sheathings of plastics; Apparatus therefor
    • B29C63/02—Lining or sheathing, i.e. applying preformed layers or sheathings of plastics; Apparatus therefor using sheet or web-like material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2011/00—Optical elements, e.g. lenses, prisms
    • B29L2011/0066—Optical filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/34—Electrical apparatus, e.g. sparking plugs or parts thereof
    • B29L2031/3475—Displays, monitors, TV-sets, computer screens
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/418—Refractive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/42—Polarizing, birefringent, filtering
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
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    • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
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    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mathematical Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Ophthalmology & Optometry (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Polarising Elements (AREA)
  • Liquid Crystal (AREA)

Abstract

The present invention relates to a polarizing plate comprising a polarizer and a polyester film formed on an upper surface of the polarizer, wherein the polyester film has a maximum thermal shrinkage angle of about 10 ° or less, and any one of a refractive index nx in an x-axis direction at a wavelength of 550nm and a refractive index ny in a y-axis direction at a wavelength of 550nm of about 1.65 or more, and a liquid crystal display device comprising the same. The polarizing plate can suppress rainbow unevenness, secure a viewing angle, improve image quality, and improve the degree of polarization and transmittance of the polarizer, thereby having excellent optical properties and a high contrast ratio.

Description

Polarizing plate and liquid crystal display device comprising same
The present invention is a divisional application of an invention patent application having an application number of 201480047525.9 and an invention name of "polarizing plate, method for manufacturing the same, and liquid crystal display device including the same", which is filed on 12.08.2014.
Technical Field
The invention relates to a polarizing plate and an optical display device comprising the same.
Background
Polarizing plates are used inside and outside the liquid crystal cell in order to control the oscillation direction of light so as to display a display pattern of the liquid crystal display device. The polarizing plate includes a polarizer and a protective film formed on at least one side of the polarizer. Generally, although the protective film is a triacetyl cellulose (TAC) film, the TAC film is more expensive than a typical polymer film. Therefore, a low-priced polymer film including a polyethylene terephthalate (PET) film is used instead of the TAC film.
A common PET film is a PET film that is stretched in a Machine Direction (MD) and/or a Transverse Direction (TD) at a certain stretch ratio in order to improve yield and has a range of phase difference, i.e., retardation. However, a common PET film stretched in the longitudinal and/or transverse directions has a high molecular orientation angle, and thus there is a large deviation between the absorption axis of the polarizer and the optical axis of the PET film. Therefore, the degree of polarization of the polarizing plate and the brightness of the screen can be reduced. Further, due to this, the Contrast Ratio (CR) of the liquid crystal display device may deteriorate. Further, the conventional PET film can reduce the degree of polarization of a polarizer and the transmittance of a polarizing plate and make the rainbow unevenness worse when exposed to high temperature for a long time. Further, when the PET film is stretched, a portion of the PET film, particularly, the terminal portion, may suffer from deterioration of optical properties due to its asymmetric molecular orientation when incorporated into the polarizing plate, and thus its use is limited. Further, because the PET film is a stretched film, the film may suffer from iridescence spots when used in a liquid crystal display device.
The prior art of the present invention is described in korean patent publication No. 2011-.
Disclosure of Invention
Technical problem
An object of the present invention is to provide a polarizing plate which can suppress rainbow unevenness, secure a viewing angle, and improve image quality.
Another object of the present invention is to provide a polarizing plate that can improve the degree of polarization and transmittance of a polarizer, thereby having excellent optical properties and a high contrast ratio.
It is still another object of the present invention to provide a polarizing plate whose polarization degree may not be deteriorated or deterioration can be minimized even if the polarizing plate is exposed to high temperature, and thus iridescence can be suppressed.
It is still another object of the present invention to provide a polarizing plate having high economic feasibility by using the stretched polyester film in all orientations as a protective film of the polarizing plate.
Means for solving the problems
Embodiments of the present invention relate to a polarizing plate including a polarizer and a polyester film formed on an upper side of the polarizer, wherein the polyester film has a maximum thermal shrinkage angle of about 10 ° or less, and any one of a refractive index nx in an x-axis direction at a wavelength of 550nm and a refractive index ny in a y-axis direction at a wavelength of 550nm of about 1.65 or more.
Another embodiment of the present invention relates to a polarizing plate including a polarizer and a polyester film formed on an upper side of the polarizer, wherein the polyester film has an absolute value of a molecular orientation angle (θ r) of about 5 ° or less.
In a particular example, the absolute value of the difference between nx and ny can be about 0.1 to about 0.2.
In particular examples, the polyester film may have a maximum thermal shrinkage of about 0.8% or less.
In a specific example, the polyester film may have an absolute value of a molecular orientation angle (θ r) of the polyester molecules based on the transverse direction of about 0 ° to about 5 °.
In particular examples, the polyester film may have a thickness of about 25 μm to about 115 μm, and a front retardance (Ro) of about 5,000nm to about 15,000nm at a wavelength of 550 nm.
In a particular example, the front retardance (Ro) can be about 10,100nm to about 12,000 nm.
In a particular example, the polyester film may be a transversely stretched film.
In a particular example, the polyester film may have a degree of biaxiality (NZ) of about 1.8 or less at a wavelength of 550nm, as represented by equation 1:
[ equation 1]
NZ＝(nx-nz)/(nx-ny)
Where nx, ny and nz are refractive indices (reactive index) in the x-axis direction, the y-axis direction and the z-axis direction of the polyester film at a wavelength of 550nm, respectively.
In a particular example, the polyester film may have a thickness direction retardation (Rth) of about 15,000nm or less at a wavelength of 550nm, as measured by equation 2:
[ equation 2]
Rth＝((nx+ny)/2-nz)×d
Wherein nx, ny and nz are refractive indices in an x-axis direction, a y-axis direction and a z-axis direction of the polyester film at a wavelength of 550nm, respectively; and d is the thickness (unit: nm) of the polyester film.
In a particular example, the polyester film may be a film formed of at least one of polyethylene terephthalate (polyethylene terephthalate), polybutylene terephthalate (polybutylene terephthalate), polyethylene naphthalate (polyethylene naphthalate), and polybutylene naphthalate (polybutylene naphthalate).
In a particular example, the optical film may be further formed to the lower side of the polarizer.
In a particular example, the optical film can have a front retardance (Ro) of about 40nm to about 60nm at a wavelength of 550 nm.
In a particular example, the optical film may be a film formed of at least one of cellulose, polyester, cyclic polyolefin, polycarbonate, polyethersulfone, polysulfone, polyamide, polyimide, polyolefin, polyacrylate, polyvinyl alcohol, polyvinyl chloride, and polyvinylidene chloride resin (polyvinylidene chloride resin).
In a specific example, the polarizing plate may have a degree of polarization of about 99.99% or more, and a transmittance of about 40% or more.
Another embodiment of the present invention relates to a method of manufacturing a polarizing plate, including: drawing the melt-extruded polyester resin at a draw ratio of about 2 to about 10 only in the transverse direction and thermally stabilizing the drawn polyester resin at about 100 ℃ to about 300 ℃ to manufacture a polyester film; and bonding a polyester film to one side of the polarizer.
In a particular example, the method further includes bonding an optical film to the other side of the polarizer.
Another embodiment of the present invention relates to a liquid crystal display device including a polarizing plate.
Technical effects
The present invention provides a polarizing plate, which can suppress rainbow unevenness, secure a viewing angle, improve image quality, and improve the degree of polarization and transmittance of a polarizer, thereby having excellent optical properties and a high contrast ratio, a method of manufacturing the same, and a liquid crystal display device including the same. In addition, the present invention provides a polarizing plate, a method of manufacturing the same, and a liquid crystal display device including the same, which may not deteriorate or may minimize deterioration in the polarization degree even if the polarizing plate is exposed to high temperature, and thus may suppress iridescence. Still further, the present invention provides a polarizing plate having high economic feasibility by using a stretched polyester film in all orientations as a protective film of the polarizing plate, a method of manufacturing the same, and a liquid crystal display device including the same.
Drawings
Fig. 1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.
Fig. 2 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.
Fig. 3 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention.
Fig. 4 is a conceptual diagram of the heat shrinkage rate in the present invention.
Detailed Description
Certain embodiments of the present invention will now be described in more detail so that they may be readily made by those skilled in the art to which the present invention pertains, with reference to the accompanying drawings. The invention may be embodied in different forms and is not limited to the following embodiments. In the drawings, elements not described with respect to the embodiments of the present invention will be omitted for clarity. The same reference numbers will be used throughout the drawings and the description to refer to the same or like elements of construction.
As used herein, terms such as "upper side" and "lower side" are defined with reference to the accompanying drawings. Thus, it should be understood that the term "upper side" may be used interchangeably with the term "lower side" or the term "lower side" may be used interchangeably with the term "upper side" when viewed from different angles.
As used herein, referring to fig. 4, the term 'heat shrinkage' may be a value obtained from B-a/a x100, in a square polyester film sample 10 having a length of about 200mm in the longitudinal direction and about 200mm in the transverse direction, a polyester film having a radius a (0< a ≦ 150mm, e.g., 100mm), equally divides the circumference of the circle 10a into a plurality of sections at the same angle a (0< a ≦ 10, particularly about 5) in a certain range from a radius 10b of the circle parallel to the longitudinal direction, to further plot a plurality of lines 10c connecting a point on the perimeter to the center of the circle and leaving the sample 10 or circle 10a at a temperature selected from the group consisting of i) at about 85 ℃ for about 30 minutes, ii) at about 100 ℃ for about 30 minutes, iii) at about 120 ℃ for about 30 minutes, and iv) a length B of the post-measurement line 10c at any one of about 150 ℃ for about 30 minutes. As used herein, the term 'maximum thermal shrinkage' means the maximum value among the measured thermal shrinkages.
As used herein, the term 'maximum heat shrinkage angle' means an angle between a radius 10b of a circle parallel to the longitudinal direction and a straight line indicating the maximum heat shrinkage rate when the angle α in fig. 4 and the heat shrinkage rate measured in fig. 4 are plotted to each other according to a point on a periphery equally divided along the angle α using the polyester film sample 10. As a result of the drawing, a drawing result having a peanut shape can be obtained.
As used herein, unless otherwise specified, 'nx', 'ny', and 'nz' are refractive indices (reactive indices) in a three-dimensional coordinate system (x-axis direction, y-axis direction, and z-axis direction (thickness direction)) of the polyester film at a wavelength of 550nm, respectively. For example, the x-axis direction may be longitudinal, or the y-axis direction may be transverse.
Hereinafter, a polarizing plate according to an embodiment of the present invention will be described in detail with reference to fig. 1.
Referring to fig. 1, a polarizing plate 100 according to an embodiment of the present invention may include a polarizer 110 and a polyester film 120 formed on an upper side of the polarizer 110, wherein the polyester film 120 may have a maximum heat shrinkage angle of about 10 ° or less, and any one of nx and ny of about 1.65 or more.
The polarizing plate in the liquid crystal display device may be exposed to high temperature for a long time. In this case, the degree of polarization of the polarizing plate may be reduced, thus deteriorating the optical properties of the liquid crystal display device. The polarizing plate according to an embodiment of the present invention may include the polyester film 120 having the maximum thermal shrinkage angle of about 10 ° or less, and thus the polarization degree and transmittance thereof are not reduced even though the polarizing plate is exposed to a high temperature. The maximum heat shrinkage angle of the polyester film may be specifically about 0 ° to about 10 °, more specifically about 0 ° to about 9 °, still more specifically about 0 ° to about 7 °, for example, 0 °,1 °, 2 °, 3 °, 4 °, 5 °, 6 °, 7 °, 8 °, 9 °, or 10 °, and more preferably closer to 0 °.
Generally, polyester films are known to have a crystallization behavior during the stretching process. Therefore, the polarizing plate using the polyester film may suffer from rainbow unevenness, thus deteriorating image quality. If both nx and ny of the polyester film are less than about 1.65, or both nx and ny are about 1.65 or more, a polarizer having the polyester film as a protective film may suffer from iridescence due to birefringence due to a change in retardation (depending on an incident angle and wavelength). However, according to an embodiment of the present invention, any one of nx and ny of the polyester film 120 in the polarizing plate is about 1.65 or more, so that it can significantly suppress the iridescence.
In one embodiment, nx may be about 1.65 or greater, specifically about 1.67 to about 1.75, and ny may be less than about 1.65, specifically about 1.45 to about 1.60. In another particular example, ny can be about 1.65 or greater, specifically about 1.67 to about 1.72, more specifically about 1.69 to about 1.72, and nx can be less than about 1.65, specifically about 1.45 to about 1.60. Herein, the absolute value of the difference of nx and ny (| nx-ny |) may be about 0.1 to about 0.2, particularly about 0.1 to about 0.18, e.g., 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, or 0.18. Thereby, the polyester film can improve the viewing angle and also suppress the rainbow unevenness.
The polyester film 120 may have a maximum thermal shrinkage of about 0.8% or less, specifically about 0 to about 0.8%, more specifically about 0 to about 0.6%, for example, 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8%, and more preferably closer to 0%. Within this range, when the polarizing plate is exposed to a high temperature for a long period of time, the problem of deterioration of the optical properties of the liquid crystal display device due to the decrease in transmittance of the polarizing plate does not occur. In an embodiment, the polyester film may have a thermal shrinkage of about 0 to about 0.8% over the entire orientation (about 0 ° to about 360 °) based on the circle of fig. 4. Within this range, the polyester film may have improved optical properties.
The polyester film 120 has an ultra-high retardation because it is stretched at a high stretch ratio, so that the polyester film can suppress rainbow unevenness when the polarizing plate is incorporated into a liquid crystal display device to prevent the polarizing plate from deteriorating the image quality. In a particular example, the polyester film 120 may have a thickness of about 25 μm to about 115 μm, and a pre-retardation (Ro) of about 5,000nm to about 15,000nm, particularly about 10,100nm to about 12,000nm, at a wavelength of 550 nm. Within the range, when the polyester film is used as a protective film of a polarizer, it can suppress iridescence. Further, it can suppress a light leakage phenomenon of light leaking from the side, and more suppress a variation in retardation depending on an incident angle to thereby prevent a retardation difference from increasing.
The polyester film 120 may have a biaxial degree (NZ) of about 1.8 or less, particularly, about 1.0 to about 1.8 at a wavelength of 550nm, as represented by equation 1. Within this range, the polyester film may have an effect of controlling iridescence due to birefringence.
[ equation 1]
NZ＝(nx-nz)/(nx-ny)
Wherein nx, ny and nz are refractive indices in an x-axis direction, a y-axis direction and a z-axis direction of the polyester film at a wavelength of 550nm, respectively.
The polyester film 120 may have a thickness direction retardation (Rth) of about 15,000nm or less at a wavelength of 550nm, for example, about 10,000nm to about 13,000nm, as measured by equation 2. Within this range, the polyester film may have an effect of controlling iridescence due to birefringence.
[ equation 2]
Rth＝((nx+ny)/2-nz)×d
Wherein nx, ny and nz are refractive indices in an x-axis direction, a y-axis direction and a z-axis direction of the polyester film at a wavelength of 550nm, respectively, and d is a thickness (unit: nm) of the film.
The polyester film 120 may have an absolute value of a molecular orientation angle (θ r) based on the transverse direction in polyester molecules of about 5 ° or less, particularly, about 0 to about 5 °, for example, 0 °,1 °, 2 °, 3 °, 4 °, or 5 °. Within this range, it can improve the polarization degree of the polarizing plate and the brightness of the screen, thereby increasing the contrast ratio thereof, and can further prevent the polarization degree of the polarizing plate from being deteriorated even if exposed to high temperature for a long period of time. The molecular orientation angle can be measured by any typical method, for example, by using KOBRA-WX100 (prince (Oji) inc.) and AXOSCAN (axome metrics) inc.).
The polyester film 120 may be any transparent film formed of a polyester resin without limitation. In an embodiment, the polyester film may be a film formed of at least one of polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, and polybutylene naphthalate resin.
The polyester film 120 may have a thickness of about 25 μm to about 115 μm. Within this range, when the film is stacked on a polarizer, the obtained product may be used as a polarizing plate.
Although not shown in fig. 1, the polyester film 120 may include a functional coating layer on its upper side, such as a hard coating layer, an anti-reflective layer, or an anti-fingerprint layer to impart functionality. The functional coating layer may have a thickness of about 1 μm to about 10 μm. Within this range, when the film is stacked on a polarizer, the obtained product may be used as a polarizing plate.
In addition, although not shown in fig. 1, the polyester film 120 may further include a side-coating layer on the underside thereof. The polyester film has a hydrophobic surface. In detail, when polyethylene terephthalate is used as the protective film, the protective film exhibits higher hydrophobicity. To apply the film to a polarizing plate, the film undergoes surface modification to convert its surface from a hydrophobic surface to a hydrophilic surface. When surface modification using sodium hydroxide (which is used for an existing cellulose film) is used for surface modification of the protective film, the surface of the protective film may not be sufficiently modified or may be damaged. To solve these problems, a surface coating layer including a high adhesion primer (primer) having hydrophobic and hydrophilic functional groups may be formed on the protective film. The primer having hydrophobic and hydrophilic functional groups may include, but is not limited to, polyester resins, polyvinyl acetate resins, or mixtures thereof. The mechanical properties and low water vapor permeability of the protective film can be maximized by adding the surface coating layer, thereby imparting high resistance to severe external conditions to the polarizing plate. In addition, a surface coating layer may be formed between the protective film and the polarizer to improve adhesion between the protective film and the polarizer.
Because the polarizer 110 has molecules aligned in a specific direction, the polarizer transmits only light in the specific direction when incorporated in a liquid crystal display device. The polarizer may be manufactured by dyeing a polyvinyl alcohol film with iodine or dichroic dye, followed by stretching it in a certain direction. In particular, polarizers are manufactured by swelling, dyeing, stretching and crosslinking processes. Each process may be performed by methods generally known to those of ordinary skill in the art.
The polarizer 110 may have a thickness of about 5 μm to about 30 μm. Within this range, the polarizer may be used for a polarizing plate of a liquid crystal display device.
Also, the polarizing plate 100 may have a thickness of about 25 μm to about 500 μm. Within this range, the polarizing plate may be used as a polarizing plate for a liquid crystal display device. The polarizing plate may have a degree of polarization of about 99.99% or more, for example, about 99.99% to about 99.999%. In addition, the polarizing plate may have a transmittance (e.g., as measured at a wavelength in the visible light range, i.e., 550 nm) of about 40% or more, for example, about 40% to about 80%. Within this range, when the polarizing plate is incorporated into a liquid crystal display device, the liquid crystal display device may not suffer from deterioration of optical properties.
Although not shown in fig. 1, an adhesive layer for a polarizing plate may be formed between the polarizer 110 and the polyester film 120 to improve the mechanical strength of the polarizing plate. The adhesive layer may comprise any typical adhesive, such as at least one of a water-based adhesive, a pressure sensitive adhesive, and a photocurable adhesive. In addition, although not shown in fig. 1, a bonding agent layer may be further formed on the lower side of the polarizer 110, thereby stacking the polarizing plate on the liquid crystal display panel. The binder may include, but is not limited to, a pressure sensitive binder.
Hereinafter, a polarizing plate according to another embodiment of the present invention will be described with reference to fig. 2.
Referring to fig. 2, a polarizing plate 200 according to another embodiment of the present invention may include: a polarizer 110; a polyester film 120 formed on the upper side of the polarizer 110; and an optical film 130 formed on the lower side of the polarizer 110. The polyester film 120 may have a maximum heat shrinkage angle of about 10 ° or less, and any of nx and ny of about 1.65 or more. The polarizing plate 200 is substantially the same as the polarizing plate 100 according to the first embodiment of the present invention, except that it further includes an optical film 130. In this way, the polarizing plate may further include an optical film, thereby enhancing its mechanical strength and minimizing the influence of the adhesive layer on the polarizer. In this regard, the optical film will be described hereinafter.
The optical film 130 is formed on one side of the liquid crystal display panel and may have a predetermined range of phase difference, thereby compensating a viewing angle. In an embodiment, the optical film may have a front retardance (Ro) of about 40nm to about 60nm at a wavelength of 550 nm. Within this range, the optical film can exhibit optimized image quality. The optical film 130 may have a thickness of about 25 μm to about 500 μm, and particularly, about 25 μm to about 50 μm. Within this range, the optical film may be used for a polarizing plate of a liquid crystal display device.
The optical film 130 is a transparent optical film, and may be a polyester film including polyethylene naphthalate, polybutylene naphthalate, and the like, or a non-polyester film. Examples of non-polyester films may include: cellulose, including triacetyl cellulose and the like; cyclic polyolefin resin, polycarbonate resin; polyether sulfone resin; polysulfone resin; a polyamide resin; a polyimide resin; a polyolefin resin; a polyacrylate resin; a polyvinyl alcohol resin; a polyvinyl chloride resin; and polyvinylidene chloride resin.
Although not shown in fig. 2, an adhesive layer for the polarizing plate may be formed between the polarizer 110 and the optical film 130 to improve the mechanical strength of the polarizing plate. The adhesive layer may comprise any typical adhesive, for example, at least one of a water-based adhesive, a pressure sensitive adhesive, and a photocurable adhesive. In addition, although not shown in fig. 2, a bonding agent layer for a polarizing plate may be further formed on the lower side of the optical film 130, thereby stacking the polarizing plate on the liquid crystal display panel. The binding agent may include, but is not limited to, a pressure sensitive binding agent.
Hereinafter, a method of manufacturing the polarizing plate according to the present invention will be described.
A method of manufacturing a polarizing plate according to an embodiment of the present invention may include stretching a melt-extruded polyester resin at a stretch ratio of about 2 to about 10 only in a transverse direction, thermally stabilizing the stretched polyester resin to manufacture a polyester film, and bonding the polyester film to one side of a polarizer.
The polyester film may be manufactured by stretching alone in the transverse direction without stretching in the longitudinal direction. Accordingly, the polyester film may have a transverse direction draw ratio of about 2 to about 10, and a longitudinal direction draw ratio of about 1 to about 1.1. Here, the "longitudinal stretching ratio of about 1 to about 1.1" means a state in which there is no additional stretching process except that the film is inevitably stretched due to the mechanical motion of the film when the film is stretched while moving in the longitudinal direction. In detail, the stretching ratio of 1 means a non-stretched state. The term 'draw ratio' as used in polyester films may mean the ratio of the length of the film after stretching to the length of the film before stretching. When the film is stretched in both the machine direction and the transverse direction at a stretch ratio of about 2 to about 10, respectively, its molecular orientation angle may exceed about 5 ° or the retardation may be too low, so that iridescence may occur.
If the transverse stretching ratio is less than about 2, the polyester film has low retardation, so that the polyester film may suffer from rainbow spots when applied to a liquid crystal display device and may be easily torn due to deterioration of physical properties. On the other hand, if the transverse stretching ratio is greater than about 10, the polyester film may be broken during the stretching process. For example, the cross-directional stretch ratio may be from about 3 to about 8.
The stretching may be performed using at least one of dry stretching and wet stretching. The stretching temperature can be from about (Tg-20) deg.C to about (Tg +50) deg.C, specifically, from about 70 deg.C to about 150 deg.C, more specifically, from about 80 deg.C to about 130 deg.C, still more specifically, from about 90 deg.C to about 120 deg.C, based on the Tg of the polyester resin. Within this range, a polyester film having the above-mentioned ultra-high retardation, a maximum thermal shrinkage rate of about 0.8% or less, and a maximum thermal shrinkage angle of about 10 ° or less may be manufactured.
The method may further comprise thermally stabilizing the stretched polyester resin after stretching the polyester resin. Polyester films stretched at high stretch ratios tend to have a restoring force that restores the film to its original state. The thermal stabilization step may control the stress on the restoring force of the polyester film, thereby maintaining thermal stability of the film. As a result, a polyester film having a maximum heat shrinkage rate of about 0.8% or less, a maximum heat shrinkage angle of about 10 ° or less, and a molecular orientation angle of about 5 ° or less can be manufactured.
The heat-stabilizing step may include heating the stretched polyester film while fixing both widthwise ends of the polyester film and moving the film in the longitudinal direction. Herein, the polyester film is stretched at a relatively low draw ratio compared to the draw ratio of the stretching step. The transverse draw ratio can be greater than about 0 to about 3 or less, specifically about 0.1 to about 2, more specifically about 0.1 to about 1. The fixing of the film in the transverse direction is performed only to an extent sufficient to prevent the film from recovering due to a high stretch ratio. There is no substantial transverse stretching (tension-relaxation) of the polyester film.
The heating in the thermal stabilization step may be performed at about 100 ℃ to about 300 ℃. Within this range, a polyester film having a maximum thermal shrinkage of about 0.8% or less, a maximum thermal shrinkage angle of about 10 ° or less, and a molecular orientation angle of about 5 ° or less can be manufactured. The heating may be performed for about 1 second to about 2 hours.
Polarizers can be made by dyeing a polyvinyl alcohol film with iodine or dichroic dyes, followed by stretching the film in a certain direction. Methods of performing such steps may be generally known to those of ordinary skill in the art.
The polyester film may be bonded to the polarizer using a typical adhesive. The adhesive may comprise at least one of a water-based adhesive, a pressure sensitive adhesive, and a photocurable adhesive.
The manufacturing method according to an embodiment of the present invention may further include bonding an optical film to the other side of the polarizer. The adhesive for bonding the optical film may include at least one of a water-based adhesive, a pressure-sensitive adhesive, and a photocurable adhesive.
The liquid crystal display device of the present invention may include a module for a liquid crystal display device including the polarizing plate according to an embodiment of the present invention. Referring to fig. 3, a module 300 for a liquid crystal display device according to an embodiment of the present invention may include: a liquid crystal display panel 310; a first polarizing plate 320 formed on an upper side of the liquid crystal display panel 310; a backlight unit 340 formed on a lower side of the liquid crystal display panel 310; and a second polarizing plate 330 formed on the lower side of the liquid crystal display panel 310 and placed between the liquid crystal display panel 310 and the backlight unit 340, wherein the first polarizing plate 320 may include a polarizing plate according to an embodiment of the present invention.
The liquid crystal display panel 310 may include a liquid crystal panel including a liquid crystal cell layer sealed between a first substrate and a second substrate. In one embodiment, the first substrate may be a Color Filter (CF) substrate (upper substrate) and the second substrate may be a Thin Film Transistor (TFT) substrate (lower substrate).
The first substrate and the second substrate may be the same or different and may be glass substrates or plastic substrates, and the plastic substrates may include polyethylene terephthalate (PET), Polycarbonate (PC), Polyimide (PI), polyethylene naphthalate (PEN), polyether sulfone (PES), Polyacrylate (PAR), and Cyclic Olefin Copolymer (COC) substrates, which may be applied to, but not limited to, flexible (flex) displays. The liquid crystal cell layer may be a liquid crystal layer including Vertical Alignment (VA) mode, In-plane Switching (IPS) mode, Fringe Field Switching (FFS) mode, and Twisted Nematic (TN) mode liquid crystals.
The second polarizing plate 330 may be a common polarizing plate and may be, for example, a polarizing plate including a polyester film, the polyester film being any one of a polyester film having a maximum heat shrinkage angle of less than about 10 °, a polyester film having any one of an x-axis direction refractive index nx at a wavelength of 550nm and a y-axis direction refractive index ny at a wavelength of 550nm of less than about 1.65, or a polyester film having an absolute value of a molecular orientation angle of more than about 5 °.
Fig. 3 shows a state where the first polarizing plate is the polarizing plate according to the first embodiment of the present invention. However, the second polarizing plate may be the polarizing plate according to an embodiment of the present invention, or both the first polarizing plate and the second polarizing plate may be the polarizing plates according to an embodiment of the present invention. Accordingly, all such aspects are encompassed within the scope of the present invention.
The first polarizing plate 320 and the second polarizing plate 330 may be respectively formed on one side of the liquid crystal display panel through a bonding agent layer (not shown in fig. 3). The binder layer can be any typical binder, for example, a pressure sensitive binder.
The backlight unit 340 is a backlight unit that is known to be used in a liquid crystal display device and may include a light source, a waveguide plate, a reflection plate, a diffusion plate, and the like.
Modes of the invention
Hereinafter, the construction and functionality of the present invention will be described in more detail with reference to preferred examples thereof. It should be noted, however, that these examples are provided for the purpose of a better illustration of the present invention and should not be construed as limiting the invention in any way.
The details of the components used in the examples and comparative examples are as follows:
(1) materials of the polarizer: polyvinyl alcohol film (VF-PS6000, Kuraray Co., Ltd., thickness: 60 μm)
(2) Polyethylene terephthalate film: the polyethylene terephthalate film had nx, ny, maximum heat shrinkage angle, and molecular orientation angle shown in Table 1
(3) An optical film: triacetyl cellulose film (KC4DR-1, Fuji Co., Japan, thickness: 40 μm)
Examples 1 to 4
The polyvinyl alcohol film was stretched at 60 ℃ to a stretch ratio of 3, iodine was adsorbed on the polyvinyl alcohol film, followed by stretching in a boric acid solution at 40 ℃ to a stretch ratio of 2.5, thereby manufacturing a polarizer. Next, a triacetyl cellulose film was stacked on one side of the polarizer using an adhesive (Z-200, Nippon Gohsei, ltd.) and a polyethylene terephthalate film shown in table 1 was stacked on the other side of the polarizer using an adhesive, thereby manufacturing a polarizing plate.
The polyethylene terephthalate films shown in table 1 were produced by melt-extruding a polyethylene terephthalate resin under the conditions listed in table 1, stretching the melt-extruded films to a stretch ratio of 6.1 in the transverse direction, not in the longitudinal direction, while mechanically moving the films in the longitudinal direction using a roller, followed by a take-up-relaxation treatment. The polyethylene terephthalate film had a thickness of 80 μm.
The maximum heat shrinkage rate and the maximum heat shrinkage angle of the polyethylene terephthalate film were measured using IM-6600 (Keyence, Inc.) according to FIG. 4. Here, a square polyester film sample having a length of 200mm in the machine direction and a length of 200mm in the transverse direction was used as the film sample. The maximum thermal shrinkage rate and the maximum thermal shrinkage angle were measured on the sample by drawing a circle (radius: 100mm, aligning the center thereof with the center of the sample), equally dividing the circumference of the circle to obtain α of 5 °, and then leaving the divided circle at 100 ℃ for 30 minutes. Ro of the polyethylene terephthalate film was measured at a wavelength of 550nm using AXOSCAN (AXOMETRICS Co., Ltd.). The molecular orientation angle of the polyethylene terephthalate film was measured using KOBRA-WX100(Oji co., ltd.) and AXOSCAN (axome electronics co., ltd.).
Comparative example 1 to comparative example 3
A polarizing plate was manufactured in the same manner as in example 1, except that a polyethylene terephthalate film having nx, the maximum heat shrinkage rate, the maximum heat shrinkage angle, and the molecular orientation angle listed in table 1 was used. The polyethylene terephthalate films in table 1 were manufactured by melt-extruding a polyethylene terephthalate resin, stretching the extruded resin under the conditions listed in table 1, followed by crystallization and stabilization treatment.
The films in comparative examples 1-2 were stretched to a stretch ratio of 6.1 in the transverse direction rather than in the machine direction. The film in comparative example 3 was stretched to a stretch ratio of 3 in both the transverse and machine directions, respectively. The polyethylene terephthalate film had a thickness of 80 μm.
TABLE 1
[ Table 1]
Figure BDA0003496692570000131
The polarizing plates manufactured in the following property evaluation examples and comparative examples were used. The results are shown in table 2.
TABLE 2
[ Table 2]
Figure BDA0003496692570000132
Figure BDA0003496692570000141
(1) Transmittance and degree of polarization: the transmittance and the degree of polarization of the polarizing plate were measured using V7100 of JASCO (JASCO) ltd. In addition, after the polarizing plate is left at a high temperature for a long time (e.g., 85 ℃ for 120 hours), the transmittance and the degree of polarization are evaluated in the same method as the above-mentioned method. Herein, the measurement is performed at a wavelength of 550 nm.
(2) Rainbow spots: the polarizing plates are respectively displaced on the upper side of the liquid crystal display panel, on the lower side of the liquid crystal display panel of the VA mode liquid crystal, and between the liquid crystal display panel and the backlight unit to be assembled. Whether or not the iris spot was generated was observed using a spectral radiometer (SR-3A, Topykang (TOPCON) Co., Ltd.). When there was no iris spot, it was evaluated as x, and when there was iris spot, it was evaluated as o. In addition, after the polarizing plate was left at a high temperature for a long time (for example, 85 ℃ for 120 hours), whether or not iridescence was generated was evaluated in the same manner as the above method.
(3) Contrast ratio: polarizing plates were respectively displaced on the upper side of the liquid crystal display panel, on the lower side of the liquid crystal display panel of VA mode liquid crystal (model name), and between the liquid crystal display panel and the backlight unit to assemble them, followed by measuring the Contrast Ratio (CR) using a luminance meter (SR-3A, Topcon ltd.). Also, the contrast ratio of the sample of comparative example 1 (which has the lowest contrast ratio) was taken as CR 0. Thus, the contrast ratio (CR/CR0) was calculated as a percentage of CR to CR 0.
As shown in table 2, the polarizing plate of the present invention did not suffer from rainbow spots, and the optical properties including the degree of polarization and the transmittance were good. In addition, even after being left at high temperatures for a long time, the polarizing plate does not suffer from rainbow spots, and optical properties including the degree of polarization and transmittance are not changed.
In contrast, in comparative example 1, the film was stretched in the transverse direction to a stretch ratio of 6.1, was not strained-relaxed, and had a maximum heat shrinkage angle of more than 10 °. Therefore, comparative example 1 did not suffer from rainbow spots, but had a poor degree of polarization. Further, even after being left at a high temperature for a long time, the polarizing plate in comparative example 1 was reduced in the degree of polarization and transmittance as compared with the present invention.
Further, in comparative example 2, the film was stretched in the transverse direction to a stretch ratio of 6.1, but the temperature range in the take-up-relaxation was not in the scope of the present invention, and any of nx and ny of the film was not 1.65 or more. Therefore, comparative example 2 suffered from rainbow spots and had poor polarization degree. The polarizing plate in comparative example 2 has a poor degree of polarization compared to the present invention even after being left at a high temperature for a long time.
Still further, in comparative example 3, the film was stretched to a stretch ratio of 3 in both the transverse and machine directions, and either of nx and ny of the film was not 1.65 or greater. Therefore, comparative example 3 suffered from rainbow spots. In addition, the polarizing plate in comparative example 3 suffered from rainbow spots even after being left at a high temperature for a long time.
Simple modifications or changes of the present invention can be easily performed by those skilled in the art. Accordingly, such modifications or changes are considered to be included in the scope of the present invention.

Claims (12)

1. A polarizing plate comprising:
a polarizer; and
a polyester film formed on an upper side of the polarizer,
wherein the polyester film has a maximum heat shrinkage angle of 10 DEG or less, a refractive index nx in an x-axis direction at a wavelength of 550nm of 1.65 or more, and a refractive index ny in a y-axis direction at a wavelength of 550nm of less than 1.65,
wherein the polyester film has a maximum thermal shrinkage of 0.6% or less,
wherein the polyester film has an absolute value of a molecular orientation angle of 5 DEG or less,
wherein the polyester film has a pre-retardation of 5,000nm to 15,000nm at a wavelength of 550nm,
the x-axis is transverse and the y-axis is longitudinal,
the polyester film has a thickness direction retardation Rth of 10,000nm to 13,000nm at a wavelength of 550nm, measured by equation 2:
[ equation 2]
Rth＝((nx+ny)/2-nz)×d
Wherein nx, ny, and nz are refractive indices in an x-axis direction, a y-axis direction, and a z-axis direction of the polyester film at a wavelength of 550nm, respectively; and d is the thickness of the polyester film, wherein d has a unit of nm,
wherein the polyester film is a transversely stretched film,
wherein the absolute value of the difference between nx and ny of the polyester film is 0.13 to 0.2.
2. A polarizing plate comprising:
a polarizer; and
a polyester film formed on an upper side of the polarizer,
wherein the polyester film has an absolute value of a molecular orientation angle of 5 DEG or less,
wherein the polyester film has a maximum thermal shrinkage of 0.6% or less,
wherein the polyester film has a refractive index nx in an x-axis direction at a wavelength of 550nm of 1.65 or more and a refractive index ny in a y-axis direction at a wavelength of 550nm of less than 1.65,
wherein the polyester film has a pre-retardation of 5,000nm to 15,000nm at a wavelength of 550nm,
the x-axis is transverse and the y-axis is longitudinal,
the polyester film has a thickness direction retardation Rth of 10,000nm to 13,000nm at a wavelength of 550nm, measured by equation 2:
[ equation 2]
Rth＝((nx+ny)/2-nz)×d
Wherein nx, ny, and nz are refractive indices in an x-axis direction, a y-axis direction, and a z-axis direction of the polyester film at a wavelength of 550nm, respectively; and d is the thickness of the polyester film, wherein d has a unit of nm,
wherein the polyester film is a transversely stretched film,
wherein the absolute value of the difference between nx and ny of the polyester film is 0.13 to 0.2.
3. The polarizing plate of claim 1, wherein the polyester film has an absolute value of a molecular orientation angle of polyester molecules based on a transverse direction of 0 ° to 5 °.
4. The polarizing plate of claim 1 or 2, wherein the polyester film has a thickness of 25 μ ι η to 115 μ ι η, and a pre-retardation of 5,000nm to 15,000nm at a wavelength of 550 nm.
5. The polarizing plate of claim 4, wherein the front retardation is 10,100nm to 12,000 nm.
6. The polarizing plate of claim 1 or 2, wherein the polyester film has a biaxial degree NZ of 1.8 or less at a wavelength of 550nm, represented by equation 1:
[ equation 1]
NZ＝(nx-nz)/(nx-ny)
Wherein nx, ny, and nz are refractive indices in an x-axis direction, a y-axis direction, and a z-axis direction of the polyester film at a wavelength of 550nm, respectively.
7. The polarizing plate of claim 1 or 2, wherein the polyester film is a film formed of at least one of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate.
8. The polarizing plate of claim 1 or 2, wherein the optical film is further formed to a lower side of the polarizer.
9. The polarizing plate of claim 8, wherein the optical film has a front retardation of 40nm to 60nm at a wavelength of 550 nm.
10. The polarizing plate of claim 8, wherein the optical film is a film formed of at least one of cellulose, polyester, cyclic polyolefin, polycarbonate, polyethersulfone, polysulfone, polyamide, polyimide, polyolefin, polyacrylate, polyvinyl alcohol, polyvinyl chloride, and polyvinylidene chloride resin.
11. The polarizing plate of claim 1 or 2, wherein the polarizing plate has a polarization degree of 99.99% or more, and a transmittance of 40% or more.
12. A liquid crystal display device comprising the polarizing plate according to claim 1 or 2.
CN202210116539.8A 2013-08-29 2014-08-12 Polarizing plate and liquid crystal display device comprising same Pending CN114397724A (en)

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US20190285789A1 (en) 2019-09-19
CN105492936A (en) 2016-04-13
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US20160209568A1 (en) 2016-07-21
US11009642B2 (en) 2021-05-18

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